1. Field of the Invention
The present invention relates to systems for aligning a towing unit with a towed unit, e.g., a trailer. In particular, the instant invention is adapted to assist the driver of the towing unit with aligning the fifth wheel hitch of a commercial truck and the king pin of a trailer to achieve positive coupling between the two, especially in zero or low visibility conditions.
2. Discussion of Related Art
To couple a vehicle, such as a commercial truck, to a trailer, the driver must continually estimate the position of the vehicle relative to the trailer while maneuvering the vehicle into alignment with the trailer. In practice, this may involve exiting the truck to determine the position of the truck relative to the trailer and then re-entering the truck to maneuver it into alignment. In addition, the driver utilizes his rearview side mirrors to approximate the lateral alignment between the truck and trailer, while vertical alignment is often judged only by "feel," or guess. Such practice often leads to high or low coupling and, possibly, lateral misalignment between the truck and the trailer, which can result in damage to the truck, trailer and/or the interlocking apparatus.
The interlocking apparatus is comprised of components on both the truck and the trailer which mate to achieve a mechanical connection. Typically, the truck is equipped with a locking assembly, known in the heavy trucking industry as a fifth wheel hitch, and an apparatus mounted to the trailer, known in the industry as a king pin. The king pin extends downwardly, perpendicular to the bolster plate to which it is attached, the bolster plate being mounted to the bottom surface of the trailer. The fifth wheel hitch includes a hitch plate having a throat with its open end facing rearwardly to receive the king pin, and a locking mechanism for locking the king pin in the throat of the hitch plate.
When backing up the towing unit, the driver often experiences difficulty in aligning the throat of the hitch plate with the king pin. For instance, the height of the king pin relative to the throat may be such that proper mating between the two will not be achieved, even though the two may be laterally aligned. In these instances, the front lower edge of the trailer may crash into the fifth wheel hitch plate (trailer and king pin too low) or the cab of the truck may crash into the body of the trailer (trailer and king pin too high). Alternatively, even though the king pin and fifth wheel hitch may appear coupled, if the king pin is not seated properly in the locking mechanism a "high couple" may result leading to an unsafe and potentially dangerous condition. On the other hand, even if the two components are at the proper engaging height relative to one another, the throat and the king pin may be laterally misaligned. In either case, positive coupling is not achieved, and the interlocking apparatus and/or the truck/trailer may be damaged or unsafe. Further, the problems attendant with this "guesswork" are exacerbated by the fact that the driver will often be faced with zero or low visibility conditions (night, severe weather, sleeper cab configurations, etc.)
As a result, systems have been developed to provide an output signal to the driver indicating the position of the truck relative to the trailer. Notably, known systems are targeted toward the "ball and hitch" coupling market and are not easily adaptable to the heavy trucking industry.
Known alignment systems use a variety of technologies to measure lateral offset and vertical alignment. Primarily, these systems utilize infrared sensor technology with a modulated pulsed beam. As such, these systems are limited in range (typically less than 20 feet) and require separate sets of infrared sensors on the towing and towed units, respectively, to indicate the lateral offset and vertical alignment. Also, because the infrared emitters and sensors are required on both the towing and towed units, the system must include a remote, powered transmitter on the towed unit. Clearly, these systems are limited in their application, inconvenient and relatively expensive.
In sum, current commercial truck/trailer coupling is performed relatively "blind" because direct observation of the king pin relative to the fifth wheel lock often is not possible. Further, systems such as air-bag suspensions lead to variable trailer and truck height, making positive coupling even more difficult. As a result, the operator relies on external reference points (trailer corner, tires, etc.) to achieve positive coupling. However, such practice often, as described above, leads to missed or incomplete or "hard coupling." These problems, and the damage often associated therewith, are worsened when the driver is faced with low visibility conditions due to cab design, darkness, weather, etc.
Therefore, the commercial trucking industry is in need of a coupling warning system that is contained in a single, relatively inexpensive unit and which is operational during varying environmental conditions. Such a system would minimize the problems associated with high or low coupling and lateral misalignment that leads to non-positive coupling and, would reduce the damage to the trailer, the truck, the fifth wheel hitch, etc.